1. Field of the Invention
Aspects of the present invention relate to a fuel cell and an electronic device including the fuel cell, and more particularly, to a fuel cell system and a mobile communication device including the fuel cell system.
2. Description of the Related Art
As Internet technologies have been continuously developed, the number of Internet users has increased, and wireless mobile communication devices have been used more frequently. Naturally, batteries with light weight, small size, and large capacity have been required for such devices. Accordingly, secondary batteries having light weight and long battery life have been desired. However, the battery life of the secondary battery is mostly standardized on the basis of standby time. Thus, in actual usage conditions, the battery life of the secondary battery is not long enough when operating time, in particular, communicating time, takes up a larger part of the battery's use. In addition, when a mobile communication device is also used as a digital camera, a camcorder, a portable memory, and/or a digital multimedia broadcasting (DMB) device, the battery life of the secondary battery is reduced.
Accordingly, fuel cells having higher power generation efficiency and total efficiency than those of the secondary batteries have been considered. Although there have not been many instances of fuel cells used in communication devices, fuel cells have been used in personal digital assistant (PDA) terminals or laptop computers.
A fuel cell is an electrochemical apparatus that transforms chemical energy of a liquid fuel into electrical energy via an electrochemical reaction. The basic principle of the fuel cell is a reaction of hydrogen, which is obtained by reforming fossil fuel such as petroleum or natural gas or by using pure hydrogen, with oxygen in the air. During the reaction, electric energy is generated, and heat and moist vapor are obtained as by-products.
The fuel cell can be distinguished from the secondary battery in that it can operate continuously as long as fuel is supplied from the outside.
Fuel cells can generally be divided into four types: phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), and proton exchange membrane fuel cells (PEMFCs). PAFCs are commercialized, and the other types of fuel cells are in an experimental stage. Also, direct methanol fuel cells (DMFCs), which directly generate electricity from methanol without reforming the fuel (hydrogen extraction), and fuel cells using metal hydride are being developed.
In case of fuel cells for mobile communication devices, oxygen is supplied to a cathode of the fuel cell through a back side of the device. However, since the back side of the device is generally covered by the hand of a user, it may be difficult to supply the oxygen when the device is being used. Moreover, it may be difficult to rapidly remove heat generated by the device, and to discharge generated CO2. In addition, a fuel tank is directly attached to an anode, and thus, when the fuel cell is mounted onto the device, the rear thickness of the device increases. Moreover, when the fuel tank is located behind a cell pack, it may be difficult to replace the fuel tank or supply the fuel.